Former United midfielder and current Under-18s boss Fletcher, who was taking interim charge of the team after Ruben Amorim's departure as head coach on Monday, saw the Reds go behind to an Ayden Heaven own goal in the first half.
His side battled back though and, after having two attempts cleared off the line, went ahead when Sesko scored twice in the first 15 minutes of the second period to turn the game on its head.
An equaliser from Burnley substitute Jaidon Anthony got the hosts back on terms entering the final quarter of the game, which we nearly netted a dramatic late winner in, when young Shea Lacey struck the crossbar in the closing stages.